For a conventional ultra-high voltage device, the concentration of the implant region below the insulation region in the structure thereof usually plays a main role in influencing the on-resistance (Rds-on). When the concentration of the implant region is high, the on-resistance (Rds-on) of the device is reduced. However, at the same time, the breakdown voltage (BV) of the device is also decreased. During mass production, the implant region having a low concentration should be adopted as the main process conditions due to requirement for a sufficiently large process window of the breakdown voltage (BV) in the device.
Although the larger process window of the breakdown voltage (BV) of the device is obtained by adopting an implant region having a low concentration, in this case, the on-resistance (Rds-on) obtained by adopting the low-concentration implant region is much higher than that obtained by adopting a high-concentration implant region in the device, affecting device performance.
Therefore, how to maintain low on-resistance (Rds-on) circumstances, while also effectively improving the process window of the breakdown voltage (BV), is the goal that the relevant industry needs to strive to achieve.